Gypsum board is a composite material made from two cover sheets with a gypsum layer typically sandwiched between the cover sheets. Typically, the gypsum layer is formed from a slurry. Gypsum boards are manufactured for use in a variety of applications with each application having specific performance requirements. The gypsum board, for example, may be applied as a structural building panel. In this application, the gypsum board may be used on internal and external walls of a structure, including areas exposed to water and moisture.
Unfortunately, the gypsum layer of the gypsum board has a tendency to absorb water. For example, the gypsum layer may absorb up to 40 to 50 parts by weight of water based on 100 parts by weight of the gypsum layer when immersed in water at about 70° F. for two hours. Absorption of water by the gypsum layer may reduce the strength of the gypsum board, increase the vulnerability of the gypsum board to microbial growth, and result in delamination of the cover sheets from the gypsum layer.
The industry has attempted to improve moisture resistance by incorporating moisture resistance components such as wax additives and silicone additives into the gypsum board. Although these additives may be effective at improving the moisture resistance of the gypsum board, each additive has its own disadvantages. For example, wax additives are required in large dosages to effectively improve the water resistance of the gypsum board. Silicone additives negatively interact with soap which is used to create voids in gypsum boards and thereby results in increased soap demand during the process. In addition, silicone additives may negatively impact air quality of the environment by increasing VOC emissions, releasing volatile low molecular oligomers and releasing hydrogen gas which is flammable.
Typically, the moisture resistance components are not completely miscible in the slurry which forms the gypsum layer. This incomplete miscibility may negatively impact moisture resistance of the gypsum board.
As such, there remains an opportunity to provide improved moisture-resistant gypsum board.